Answer:
x = 20
Explanation:
The sum of the three angles in the diagram is 180 degrees since they form a straight line
x + 100 + 3x = 180
Combine like terms
100 +4x = 180
Subtract 100 from each side
100+4x-100 =180-100
4x= 80
Divide each side by 4
4x/4 = 80/4
x = 20